In general, through a wired or a wireless communication network, digital TV service provides various services that conventional analog broadcasting service cannot provide. For example, IPTV (Internet Protocol Television) service, which is one kind of digital TV service, provides interactivity by which the user can actively choose a program to watch, time to watch, and so forth. Based on such an interactive feature, IPTV service can also provide various additional services such as Internet search, home shopping, online game, and so forth.
To use the IPTV service, the user should be equipped with an IPTV set-top box. An IPTV set-top box is loaded with software supporting an interactive service and based on the software, carries out functions as a service client. For example, an IPTV set-top box requests transfer of broadcasting contents from a service provider while communicating with the service provider through an IP network and converts broadcasting signals received from the service provider into standard TV signals, transmitting the converted signals to TV receivers.
Meanwhile, associated companies are making an effort to expand service area of IPTV contents by linking IPTV service with the home network environment. Contents sharing service is one example of such effort. The contents sharing service associates an IPTV set-top box, which is an IPTV compatible terminal, with devices connected to the home network and redistribute the contents stored in the IPTV set-top box among the associated devices. Therefore, the contents sharing service enables the user to play IPTV contents at various devices preferred by the user.
One of the most important issues in implementing a system which provides the contents sharing service is to protect contents from illegal acts that can occur during sharing of contents, e.g., illegal leakage or copy of contents. In that regard, a security means or procedure for protecting contents is necessary in case of providing contents sharing service. Therefore, immediate development of security technology related to contents sharing service is required.